Four-way switches are well known in the art which use a housing and a central movable-contact assembly which registers with a lower fixed-contact assembly. Such switches are typically used to operate a pair of adjustment motors for an electrically-adjusted vehicle mirror. In a typical prior art construction, the movable-contact assembly comprises a handle, a pivotable rocker member, four orthogonally disposed contact pins projecting downwardly from the rocker, and a spring-loaded contact on each pin. The movable-contacts register with four corresponding fixed output contacts in a base and thus are themselves orthogonally disposed. A first power contact is central to the fixed output contacts and a second power contact of annular configuration surrounds the four fixed output contacts. In the prior art structure, the first or central power contact is connected to battery negative and the second or surrounding annular contact is connected to battery positive. Upon movement of the handle, the rotor pivots to move two of the four movable-contacts from sole engagement with respective ones of the four fixed output contacts so that the base of one movable-contact bridges one fixed output contact and the central power contact and so that the base of the other movable-contact bridges the diagonally-opposed fixed output contact and the annular power contact. Thus, the source of electrical power is connected to the selected two of the fixed output contacts whereby an adjustment motor connected to those contacts may be driven by the source of power. If the handle is moved in an orthogonal direction, the other two movable-contacts are caused to bridge the other two fixed output contacts to the central power contact and the outer annular power contact, respectively. Since there are four directions of movement of the handle, there are four unique connections of the contact members allowing each of two adjustment motors to be connected to the power supply with two different polarities of connection to be thereby driven in two directions.
The present switch is a four-way switch generally of the above design. However, there are important differences as will be described.
One important feature of the present invention is the utilization of a die-cast housing to form one of the power contacts, and particularly, the ground contact of the switch. By this means, the provision of a separate ground contact is avoided. To facilitate the use of the die-cast housing as a contact of the switch, several important advances have been made. For example, the die-cast housing is designed so that the movable-contacts are caused to engage the die-cast housing substantially above the base of the movable contact. Additionally, the die-cast housing has been provided with a pair of projections forming a V-shaped valley between the projections which receives the movable-contact when it makes engagement with the housing. The valley is so configured with respect to the diameter and configuration of the movable-contact so that the movable-contact will be biased into electrical engagement with the housing at two points with a sliding motion. By providing two points of contact, a redundant point of contact is established. Additionally, the sliding motion provides a wiping action which reduces the buildup of insulating oxide on the respective engaging surfaces of the contacts. Additionally, a clearance between the contact pins and the movable-contact is established which allows a slight rocking action of the contact on the pin so as to assure that the contacts do not lift off of the fixed-contact surfaces when a greater than normal operating force is applied to the operating handle.
The present switch has several other novel features. For example, a contact insulating member is provided with guideways for the movable-contacts which assure that the movable-contacts move along a path defined by the guideways during operation of the switch. Additionally, a printed circuit board is provided which incorporates several important features. Firstly, the fixed-contacts are disposed on the upper surface of the circuit board and electrically connected to a conductive foil in a circuit pattern on the lower surface of the circuit board. A wiring harness for connection of the switch to the adjustment motors is also electrically connected to the conductive foil of the circuit board. Furthermore, the circuit board mounts and interconnects a double-pole, double-throw switch which is used to select either the right or left mirror of the vehicle. As a further feature of the invention, provision is made for grounding the circuit board directly to the die cast housing by providing a shoulder on the die cast housing which engages the conductive foil on the lower surface of the circuit board. As a still additional feature of the present invention, a novel mechanical strain relief is provided in the form of an offset between adjacent passages for the conductors which clamps the conductors when the switch is assembled.
An alternate embodiment is disclosed which provides two points of contact between each movable switch contact and the central supply contact. The alternate embodiment also provides two points of contact between each movable switch contact and the fixed output contacts. This is accomplished by providing the central supply contact with a cruciform shape and the fixed output contacts with a dished upper surface. Of course, the two points of contact in each instance enhances the reliability of the switch of the present invention.